It is well known that iodine is one of the best decontaminating agents known. It is readily available, either as elemental iodine or more commonly in the form of potassium iodide, and has proved effective against Gram Positive and Gram Negative bacteria, fungi, spores and viruses. Thus, the addition of iodine or a form thereof from which iodine will be released is known as an effective way to decontaminate fluids, which term includes both liquids and gases.
However, while iodine is an essential element in human diet, its presence in a fluid, particularly in water in quantities sufficient to kill bacteria and viruses. will be offensive and render the water undrinkable. Iodine has an unpleasant odor and tends to impart a yellowish brown color to water and other fluids. So, after iodine has been in contact with a fluid to be decontaminated and has accomplished its purpose as a bactericide, the problem remains as to how to remove the iodine from the fluid, in the case of water, so that the water can be rendered potable. While some iodine is necessary in the human diet, excess iodine irritates animal tissue and can be poisonous.
It has thus become necessary to find a simple way to remove iodine from a solution or fluid after the iodine has accomplished its decontaminating function, and the use of a nylon polymer to perform this function has been recognized. That prior art with which the present inventor is familiar is U.S. Pat. No. 4,888,118 to Carl E. and Arthur C. Barnes. Such patent discloses that iodine may be used for the treatment of water, and that the iodine may thereafter be removed from the water/iodine solution by complexing it with nylon-4. Nevertheless, in what might appear to be a contradiction, Barnes also discloses that iodine may be introduced into impure water by the use of a nylon-4/iodine complex, i.e., an iodophor., and Barnes cites to Canadian Patent No. 1,119,748 for the disclosure of the use of a nylon-4/iodine complex as the source of iodine to destroy microorganisms and make the water potable. Indeed, it is clear from the Barnes's disclosure that the use of a nylon-4 iodophor is their preferred manner of adding iodine to contaminated water.
As Barnes explains, and as I have confirmed, the use of nylon-4 to sequester iodine, as opposed to utilizing it to supply iodine to a solution, presents a problem. When the iodine concentration is very low compared to a considerable excess of nylon-4 polymer, the equilibrium will swing in favor of the iodophor complex. However, when the system is more heavily loaded with iodine, e.g., perhaps 5% iodine, an equilibrium will be established in which a substantial quantity of iodine is left in the water. This is a situation that is highly undesirable, because the water treated with the nylon-4 polymer will have a taste and color from the iodine, making it undesirable for drinking purposes. The only solution would be to use large quantities of nylon-4 polymer, an event that could make the entire procedure impractical.
It is, therefore, a primary object of the present invention to provide a method of utilizing a polymer to sequester decontaminating iodine from a fluid, usually water, in which the polymer complexes with the iodine and the complex has such a slow release of iodine that it and its complexed iodine can be removed from the fluid before the substantial release of iodine from the complex.
As a solution to the problems present through the use of a nylon-4 iodophor to complex iodine, it has been determined that the iodine in the solution should have such a slow release of iodine that equilibrium between the polymer and iodine, at which equilibrium substantial quantities of iodine may be present in the solution, will not be released until well after the iodophor complex has been removed from the solution, thereby preventing the release of iodine from the complex to the fluid, as is the case with the nylon-4 iodophor disclosed in the Barnes patent.